This invention relates generally to the field of methods of manufacture pallets used to support heavy items or equipment, or large numbers of discrete items such as bags or boxes, for movement by a handtruck or forklift, and more particularly to such pallets made of metal rather than wood. Even more particularly, the invention relates to the manufacture of metal pallets where the deck member is formed by intersecting members in a grid or grate pattern, and where the technique of pressure resistance welding is utilized.
Pallets for supporting objects are well known. The most common pallet is wooden and comprises two planar deck members composed of sheets or individual slats, the deck members being separated by upright supports to allow for insertion of the tines of a handtruck or forklift between the deck members so that the pallet can be raised and moved to a different location. Another common pallet construction utilizes a single deck member supported by legs, the legs properly spaced to allow for insertion of the tines beneath the deck member. Wooden pallets, while cheap to manufacture, have a limited life under the best circumstances, are readily susceptible to damage and decay, are difficult to dispose of or recycle, and have limited support capacity To solve these problems, metal pallets have been developedxe2x80x94the metal material providing longer life, less likelihood of damage and degradation, and increased support capacity. A problem with metal pallets is that the pallet itself is heavier and the materials and methods of construction are costlier than for a wooden pallet. To address the weight issue, metal pallets have been developed where the deck member is formed by intersecting bars or rods to define or grid or grate as the upper surface rather than having a solid or extended upper surface to bear the goods. Examples of these pallets are seen in U.S. Pat. No. 2,652,219 to Arthur, U.S. Pat. No. 3,756,167 to Wilson and U.S. Pat. No. 4,323,016 to Flesher et al. Arthur and Wilson perpendicularly weld a layer of parallel rods across a sub-layer of parallel rods, while Flesher et al. shows intersecting square profile members. A problem with each of these is that the tops of the intersecting members used to create the grid or grate are not even, such that the upper surfaces of the members running in one direction are higher than the upper surfaces of the members running in the other direction. This creates a deck member with an upper surface likely to snag the objects placed thereon whenever the objects are slid across its surface. One solution to this problem is illustrated in U.S. Pat. No. 4,690,360 to Looker, where a thin sheet is affixed across the intersecting members, but this construction adds unnecessary weight to the pallet.
It is an object of this invention to provide a metal pallet construction where the deck member of the pallet is formed as a grid or grate by intersecting a plural number of parallel rod members perpendicularly with a plural number of parallel flat bar members positioned on edge such that an elongated thin edge of each flat bar member is its upper surface, where the upper surface of the deck member is flat and planar and the upper surfaces of the rod members are even with the upper surfaces of the flat bar members, in that the rod members are joined to the flat bar members by pressure resistance welding such that a portion of the thin edge of the flat bar member is melted and the rod member is pushed into the flat bar member to create a flush upper surface deck member in all directions.
The invention is a metal pallet, and its method of manufacture, for supporting relatively large loads a short distance above the ground or floor such that the pallet can be lifted and moved by a handtruck or fork lift, and comprises in general a deck member formed by perpendicularly intersecting a plural number of parallel rod members and a plural number of parallel flat bar members, where the flat bar members are positioned on edge such that one of the elongated thin edges defines the upper surface of the deck member in combination with the rod members, the rod and flat bar members forming a grate or grid enclosed by a peripheral framing edge member and preferably an outer frame member. Horizontally disposed skid members are connected to the deck member by skid uprights attached to the outer frame and interior uprights joined between adjacent flat bar members by a bridging member, to create a space to receive the tines of the handtruck or fork lift. The rod members are connected to the flat bar members using a pressure resistance welding technique, where the metal of the flat bar member is melted at the junction point and the bar member is pressed into the flat bar member such that the upper edge of the flat bar and the top of the round bar are flush and form a substantially flat and planar upper surface on the deck member in all directions.